There exists a need in the medical field for an improved system for carrying out the percutaneous implantation of biological venous valvular replacements for human valves and in particular cardiac valves. Up until recently, many valves such as heart valves had to be replaced surgically. Accordingly, the patients were exposed to all the potential dangers of major surgery.
Recently, procedures have been devised for implanting biological valves harvested from animals percutaneously into humans to replace damaged or malfunctioning valves. Andersen et al. in U.S. Pat. No. 5,840,081 describes a system for carrying out such a procedure. In Andersen et al., a biological cardiac valve is mounted upon the expandable stent of a catheter. The assembly is crimped onto the balloon section of the catheter and a protective cap is placed over the package. The catheter is then passed through a body lumen into a predetermined site within the heart. The package is then moved out of the cap and is positioned in the implantation site using well known positioning techniques. The balloon is inflated causing the stent with the replacement valve attached thereto to expand thus implanting the valve within the desire site.
The Andersen et al. type system works well in practice in that it can be carried out in a relatively short period of time when compared to surgical procedures and the risk to the patient is considerably reduced. However, the biological prosthesis that include the venous valvular replacement and the stent tends to be relatively bulky and thick even when tightly compressed against the deflated balloon and thus sometimes difficult to move through the body lumen into the implantation site. Most catheters in present day use can not deliver the necessary torque to guide the prosthesis through the body lumen, particularly where there is a relatively tight bend in the path of travel. In addition, most of the catheters that are equipped with protective caps do not possess the rigidity needed to hold the prosthesis in the desired location as the balloon is cleared for inflation.